Polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants that possess toxic, mutagenic and carcinogenic properties. A considerable amount of research effort has been directed towards studies on the mammalian oxidation of this class of compounds. However, almost nothing is known about their interaction with microorganisms. The major objective of this research proposal is to elucidate the mechanisms used by bacteria and fungi to oxidize benzo[a]pyrene, benzo[a]anthracene and 3-methylcholanthrene. Such studies will involve the disciplines of chemistry, biochemistry and enzymology and should provide information relative to the fate of these compounds in the environment and the development of methods for their removal. In addition, basis information relevant to studies on the metabolism of carcinogenic hydrocarbons by higher organisms will also be obtained. Studies on the degradation of benzo[a]pyrene, benzo[a]anthracene and 3-methylcholanthrene by bacteria will involve the isolation of mutant strains that accumulate degradation products. Each metabolite will be isolated and identified by modern chemical techniques. The unique enzyme(s) responsible for initiating the oxidation of carcinogenic hydrocarbons will be purified and their mechanism of action elucidates. Cytochrome P-450 and epoxide hydrolase will be purified from cells of the filamentous fungus, Cunninghamella elegans. The purified enzymes will be used to probe the anatiomeric specificity involved in the formation of carcinogenic metabolites from benzo[a]pyrene.